In this video, NewsHour Science Unit correspondent Spencer Michels looks how politics can get in the way of fixing important infrastructure problems. He reports from San Francisco where engineers and politicians have battled over how to fix the earthquake-prone San Francisco Bay Bridge.

The Bay Bridge is just one of 72,000 American bridges that need repairs across America. After 20 years of political wrangling over the size, look and cost of permanently repairing weak points of the bridge's span, officials have finally agreed to build a new bridge next to the old one, eventually tearing the old one down.

While some politicians like former San Francisco mayor Willie Brown have focused on the need for a bridge to be visually appealing, structural engineers cite the need for a sound structure.

Engineer Bart Ney remarked, "We're engineers. A to B sounded good to us, but the community really stepped up and said that they wanted something more at this juncture."

"What was originally a limited objective, which was to build a new span that would be seismically strong, grew into a monstrosity where every interest group under the sun tried to glom onto the project and achieve their objective. They all got in the way of getting this project done sooner." - Steve Heminger, Metropolitan Transportation Commission

"It's almost impossible at the state level to do what you can do at a city level. At a city level, you actually can say, 'By this date, we're going to start,' and we actually start. At the state level, you've got a state legislative body. You've got the governor. You've got the infrastructure, political types, made up of Caltrans and others, and they kind of work at their own pace." Willie Brown, former San Francisco mayor

1. Who pays to build and maintain roads and bridges?

2. What forms of transportation do you and your family use most often?

1. How does it make you feel to know you could be driving over bridges awaiting permanent repairs?

2. Who should be responsible for paying to improve roads and bridges, the state government or the federal government? Why?

3. If you were a state leader and needed to prioritize the different spending costs for your state, how would repairing infrastructure rank against other costs like education, health care and emergency services?

4. In the video, former San Francisco mayor Willie Brown talked about how city residents are looking for a bridge that is visually attractive. Why would that be important to a city? Is this something politicians and engineers should think about?